This invention relates to fastener driving devices and, more particularly, to fastener driving devices of the portable type.
Portable type fastener driving devices of the type herein contemplated are the type that include a portable frame structure having nosepiece structure defining a fastener drive track, a fastener driving element slidably mounted in the drive track, a magazine assembly for feeding a supply of fasteners along a feed track so as to move a leading fastener into the drive track and a manually actuated fastener driving system for moving the fastener driving element through successive cycles each of which includes a drive stroke and a return stroke. The driving system usually involves some sort of power, such as a spring, electricity, combustible gases, or air under pressure. In the last four power modes, it is important to prevent inadvertent or unwanted power actuations. To this end, it is usual that actuation by the normal digitally moved trigger member is modified by the action of a work contact assembly which is actuated when the user moves the device into working relation with a workpiece. An enabling member is provided which cooperates with the actuating member, trigger member and work contact assembly to effect movement of the actuating member to actuate the power only if both the trigger member and work contact assembly are actuated.
In some arrangements, which have been referred to as concomitant arrangements, power actuation is made to occur when both actuations occur without regard as to which is first. Other arrangements have been referred to as sequential arrangements. In the sequential arrangement, power actuation will only occur when the work contact assembly is first actuated and then the trigger is actuated.
One problem that can occur even in sequential arrangements is that the recoil of the device can result in an unwanted double firing. This recognized problem has been dealt with in prior art arrangements, as, for example, in U.S. Pat. No. 5,669,541, the disclosure of which is hereby incorporated into the resent specification.
The arrangement disclosed in the ""541 patent is an arrangement which can be selectively manually converted into either a concomitant operation mode or a sequential operation mode. In the sequential mode, the arrangement provides an intermediate enabling member which is pivotally mounted on the trigger member in a position so that a free end thereof will be moved up in a pivotal movement about its pivotal axis with the trigger member from a first position into a second position when the work contact structure is moved. This pivotal movement is insufficient to effect actuation which is accomplished when the trigger member is thereafter sequentially moved into an actuating position. The actuating position does not correspond to the final operative limiting position into which the trigger can be moved. Instead, there is provided a deliberate small amount of movement after the actuating position is reached before the trigger movement is stopped by arriving at its operative limiting position. His last small movement is used to move the free end of the rocker member out of contact with the work contacting structure so that it can be spring biased into an interim position out of the path of movement of the work contacting structure. Consequently, when the trigger member is in its operative limiting position at the end of a normal sequential actuating movement, the enabling member will be in the interim position out of the path of movement of the work contacting structure. In this way, double firing is prevented.
Applicant has found that an arrangement of this type is difficult to get into proper adjustment during assembly and tends to get out of adjustment once established. The amount of travel of the trigger beyond the actuating position must be enough to effect disengagement of the end of the rocker member with the work contact structure. Even so, the final movement is a relatively small amount of the total movement which must be manually imparted to the trigger. In terms of time, the final movement is accomplished almost instantaneously after actuation is commenced even before recoil occurs. There is a need to provide an arrangement by which double firing can be effectively prevented without requiring the delicate balance inherent in the operation of the prior art arrangement.
It is an object of the present invention to fulfill the need discussed above. In accordance with the principles of the present invention, this objective is obtained by providing a fastener driving device comprising a frame structure presenting a handle portion constructed and arranged to be gripped by a user enabling the user to handle the device in portable fashion. Fixed with respect to the frame structure is nosepiece structure defining a fastener drive track. A fastener driving element is slidably mounted in the drive track. A manually actuated fastener driving system is carried by the frame structure which is constructed and arranged to move the fastener driving element through successive operating cycles each including a drive stroke and a return stroke. A magazine assembly is carried by the frame structure and has fixed structure defining a fastener feed track leading to the drive track and movable structure constructed and arranged to enable a package of fasteners to be loaded in the magazine assembly and fed along the feed track so that the leading fastener of the fastener package is moved into the drive track so as to be driven outwardly thereof into a workpiece during the drive stroke of the fastener driving element.
An actuating member is constructed and arranged with respect to the frame structure to be moved rectilinearly in a direction generally parallel with the drive track between a normally biased inoperative position and an operative limiting position thereabove. A trigger member is constructed and arranged with respect to the frame structure to be manually pivoted between an inoperative position and an operative position thereabove. A work contact assembly is constructed and arranged with respect to the frame structure to be moved from a normally biased inoperative position into an operative position in response to the movement of the device into cooperating engagement with a workpiece. The work contact assembly includes an upper structure movable along a generally rectilinear path between an inoperative position corresponding with the inoperative position of said work contact assembly and an operative position thereabove corresponding to the operative position of said work contact assembly. An enabling member has one end pivotally connected to the trigger member, an opposite end operatively associated with an upper end of the upper structure and a central portion disposed below a lower end of the actuating member. A spring is constructed and arranged with respect to the enabling member and the frame structure to bias the enabling member into a normal inoperative limiting position with respect to the trigger member.
The opposite end of the enabling member is constructed and arranged with respect to the upper end of the upper structure, so that when the enabling member and the trigger member are in the inoperative positions thereof, movement of the upper structure from the inoperative position thereof into the operative position will move the opposite end of the enabling member through a first arcuate path into a first position of the enabling member during which the central portion thereof in inoperable to move the actuating member into the operative position thereof. The enabling member when in the first position is constructed and arranged to move into a second position in response to the manual movement of the trigger member into the operative limiting position thereof during which the central portion of the enabling member is operable to move the actuating member into the operative position thereof.
When the enabling member is in the second position and the trigger member is retained in the operative limiting position thereof, the enabling member will be moved into a third position in response to a predetermined movement of the upper structure toward the inoperative position thereof either by virtue of the normal rebound of the device at firing or by a manual movement of the device away from the workpiece.
The opposite end of the enabling member is movable through a second arcuate path during the movement of the enabling member from the second position thereof into the third position thereof so as to be out of the rectilinear path of the upper structure if the upper structure is moved back into the operative position thereof while the trigger member is retained in the operative limiting position thereof. The opposite end of the enabling member when the enabling member in the third position being biased to move through a third arcuate path by the release of the trigger member from the manual movement thereof into the operative limiting position thereof. The third arcuate path of movement of the enabling member is configured to move the opposite end of the enabling member (1) into a position overlying the upper end of the upper structure when the upper structure is disposed in the inoperative position thereof and (2) into abutting engagement the said upper structure when the upper structure is in the operative limiting position thereof.
By establishing a relationship between the enabling member, the trigger member and the work contacting upper structure in which the event that initiates the return stroke of the fastener driving element is the recoil itself rather than a prior manual trigger member movement, double firing is prevented without the necessity of dealing with the highly critical timing balance heretofore required.
Other objects of the present invention are to provide a device of the type describe above which is combined with other features hereafter described in detail.